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Article
Power Doppler Ultrasonography of the
Feeding Arteries of the Prostate Gland
A Novel Approach to the Diagnosis of Prostate Cancer?
Ahmet Tuncay Turgut, MD, Esin Ölçücüoğlu, MD,
Pınar Koşar, MD, Pınar Özdemir Geyik, PhD,
Uğur Koşar, MD, Vikram Dogra, MD
Objective. The purpose of this study was to assess the role of spectral Doppler ultrasonographic
parameters of the feeding arteries of the prostate for the detection of prostate cancer. Methods. A
total of 55 patients referred for prostate biopsy with a mean age of 66.4 years (range, 46–82 years)
were included. In each patient, Doppler indices from bilateral capsular and urethral arteries were
obtained. The indices were compared with regard to malignant (group A) and benign (group B) subgroups of histopathologic outcomes of transrectal ultrasonographically guided prostate biopsy for each
side (n = 19 and n = 91 for groups A and B, respectively) and to assess whether the indices were significantly altered on the side with cancer compared with the contralateral side. Results. The mean pulsatility index value for the capsular artery of group A (1.49 ± 0.57) was significantly lower than that of
group B (1.71 ± 0.52; P = .048). The mean resistive index and systolic/diastolic ratio for the capsular
artery of group A (0.78 ± 0.10 and 5.40 ± 2.74, respectively) were lower than those of group B (0.82
± 0.08 and 7.40 ± 4.91) despite being statistically insignificant (P = .075 and .119, respectively).
Conclusions. Spectral waveform measurements by power Doppler transrectal ultrasonography may be
useful in differentiating prostate cancer from benign hypertrophy. Further research is needed to elucidate the potential of spectral Doppler indices of the capsular and urethral arteries. Key words:
prostate; prostatic neoplasms; transrectal color Doppler ultrasonography.
Abbreviations
BPH, benign prostatic hyperplasia; CDUS, color
Doppler ultrasonography; HGPIN, high-grade prostatic
intraepithelial neoplasia; PCa, prostate cancer; PDUS,
power Doppler ultrasonography; PI, pulsatility index;
PSA, prostate-specific antigen; RI, resistive index; S/D,
systolic/diastolic; TRUS, transrectal ultrasonography
Received February 12, 2007, from the Department of
Radiology, Ankara Training and Research Hospital,
Ankara, Turkey (A.T.T., E.Ö., P.K., U.K.); Department
of Biostatistics, Hacettepe University, Faculty of
Medicine, Ankara, Turkey (P.Ö.G.); and Department
of Imaging Sciences, University of Rochester School
of Medicine, Rochester, New York USA (V.D.).
Revision requested February 14, 2007. Revised
manuscript accepted for publication March 8, 2007.
This study was presented at the 2007 American
Institute of Ultrasound in Medicine Annual
Convention, March 15–18, 2007, New York, New
York. The preliminary findings of this study were presented at the 13th European Symposium on
Urogenital Radiology, September 8–11, 2006, Cairo,
Egypt.
Address correspondence to Ahmet Tuncay Turgut,
MD, 25. Cadde, 362. Sokak, Hüner Sitesi 18/30,
Karakusunlar, 06530 Ankara, Turkey.
E-mail: ahmettuncayturgut@yahoo.com
T
he use of color Doppler ultrasonography (CDUS)
as a noninvasive means for displaying the vascular
anatomy of the prostate gland produces a realtime, reproducible, and symmetric flow pattern.
In early studies, it was reported that color flow intensity is
generally low or absent in the normal prostate, and focal
hypervascularity in the peripheral zone should be regarded as suspicious for malignancy despite the fact that
inflammatory lesions have a similar vascularization pattern.1,2 Recently, remarkable progress in CDUS technology has increased the sensitivity for identifying and
describing normal vascular anatomy in the peripheral
zone of the prostate.3 It has been shown that blood flow
to the prostate is supplied mainly by the capsular and
urethral branches of prostatic arteries, supplying two
thirds and one third of the glandular prostate volume,
respectively.3 Both capsular and prostatic arteries mainly
course along the posterolateral border of the prostate,
sending branches that perforate the capsule and enter
© 2007 by the American Institute of Ultrasound in Medicine • J Ultrasound Med 2007; 26:875–883 • 0278-4297/07/$3.50
Power Doppler Ultrasonography of Prostate Gland Feeding Arteries
the peripheral zone. The urethral arteries, conversely, course parallel to the prostatic urethra after
they enfold into the prostate at the bladder neck.3
Power Doppler ultrasonography (PDUS), which
has high sensitivity for displaying particularly
slow blood flow, has the capability to depict the
number, course, and continuity of vessels more
readily than other imaging methods.4 Apart from
the improved sensitivity to slow flow, PDUS has
the advantages of relative angle independence
and, potentially, a more accurate depiction of tissue perfusion.5 In general, PDUS has been
reported to have 3- to 4-fold higher sensitivity to
blood flow compared with CDUS alone.6,7
Moreover, PDUS has been reported to be superior to conventional CDUS in revealing normal
renal8 and prostatic5 vasculature.
To date, consensus has not been reached on a
single test or procedure as an efficient means for
diagnosing prostate cancer (PCa) at an early and
potentially curable stage, although several methods have been proposed, including digital rectal
examination, the serum prostate-specific antigen
(PSA) test, percent free PSA, and transrectal ultrasonography (TRUS).9 On the other hand, the main
emphasis of prostate examinations with CDUS
and PDUS has long been the differentiation of PCa
from benign processes such as benign prostatic
hyperplasia (BPH) and prostatitis by focusing on
the tumor vascularity, rather than investigating
the capability of the modalities to detect the
changes in the vascular architecture secondary to
the aforementioned disease processes.
In this study, we aimed to assess the role of
spectral Doppler parameters such as the pulsatility index (PI), resistive index (RI), and systolic/diastolic (S/D) ratio for the detection of PCa
in urethral and capsular arteries, which are the
main feeding arteries of the transition and
peripheral zones of the prostate, respectively. To
our knowledge, a study in which the spectral
Doppler indices of capsular and urethral arteries
were measured by PDUS to evaluate PCa has not
been reported previously.
Materials and Methods
Fifty-five male patients referred for TRUS-guided
prostate biopsy because of suspicious digital rectal examination findings, an abnormally elevated
876
serum PSA level (>2.6 ng/mL), or abnormal
TRUS findings were included in the study. Fortythree patients had biopsies for the first time,
whereas the other 12 had repeated biopsies. The
study was approved by our hospital’s Training
Board, and all patients included in the study gave
informed consent. The patients received 500 mg
of ciprofloxacin every 12 hours on the day before
the biopsy and were asked to continue the antibiotic prophylaxis every 12 hours on the day of the
procedure and the following 3 days. In addition,
they received a cleansing Fleet enema (Fleet
Laboratories, Lynchburg, VA) on the morning of
the procedure. The probe used for the examination was covered by 2 sheaths with adequate
lubrication gel before being inserted into the
anus.
Before the sampling procedure, a gray scale and
color Doppler TRUS examination of the prostate
gland was performed with the patients lying on
the examination table in the left lateral decubitus
position with the knees flexed. The ultrasonographic evaluation was performed with a CDUS
scanner (SDU-2200; Shimadzu Corporation,
Kyoto, Japan) equipped with a biplane 4- to 8MHz transrectal probe. The examinations were
performed by 2 radiologists (A.T.T. and E.Ö.)
experienced in TRUS imaging of the prostate and
blinded to the preprocedural rectal physical
examination and PSA studies. The parenchyma
of the gland was evaluated in axial and sagittal
planes for any abnormality of the echo texture.
After the dimensions were measured in 3 planes,
the prostate volume was automatically calculated by the machine using the following ellipsoid
formula: volume of prostate = 0.52 × td × apd ×
ccd, where td represented the transverse diameter of the prostate; apd, the anteroposterior
diameter of the prostate; and ccd, the craniocaudal diameter of the prostate.
During PDUS examination of the prostatic vasculature, the blood flow in the capsular and urethral arteries on each side was analyzed in the
largest transverse section of the prostate (Figure
1) in accordance with reports by Rifkin et al1 and
Neumaier et al.3 The capsular arteries, preferably
apposed to the neurovascular bundle, were
examined at the point where they entered the
prostate, rather than the intraprostatic branches
penetrating into the gland. At the same plane,
J Ultrasound Med 2007; 26:875–883
Turgut et al
urethral arteries coursing parallel to the urethra
were displayed as symmetric, elongated, and
straight vessels within paramedian sites of both
lobes. During the whole ultrasonographic study,
care was taken to avoid excess probe pressure on
the rectal wall. In addition, each patient was
asked to empty his urinary bladder to preclude
compression of the intraprostatic vasculature.
Furthermore, each patient was instructed to suspend breathing temporarily during the examination to minimize flash artifacts secondary to the
motion of the prostate by respiratory movements.
The power Doppler gain was set to just below
the threshold to make the capsular and urethral
arteries identifiable with the least background
noise. Spectral waveform analysis was performed after the blood flow samplings were
performed. Thereby, the mean values of PI, RI,
and S/D ratio were calculated after 3 consecutive measurements were performed, with the
spectral waveforms being stable in 5 pulses.
Meanwhile, focal areas of increased vascularity
or those with an abnormal echo texture (eg,
hypoechoic or heterogeneous) within the peripheral zone of the prostate were accepted as suspicious for malignancy.
All patients received periprostatic local anesthesia immediately before the biopsy procedure.
A total of 10 mL of 2% lidocaine (5 mL on each
side) was injected by a 22-gauge Chiba needle
under TRUS guidance in a sagittal view to the
region of the periprostatic neurovascular bundle
at the base of the prostate just lateral to the junction between the prostate and the seminal vesicles. The systematic sampling of the prostate was
performed with an 18-gauge, 20-cm spring-loaded biopsy needle. In every patient, biopsies were
taken from ultrasonographically detectable suspicious areas in the peripheral zone in addition
to the standard 12-core sampling. For repeated
biopsies, 4 cores from the inner gland and 2 from
each side were sampled as well. For each patient,
the histopathologic outcome of the biopsy specimen from each lobe of the prostate was noted.
The study group was further divided into 2 subgroups (groups 1 and 2, according to malignant
and nonmalignant histopathologic findings),
which were compared statistically for the mean
values of patient age, total PSA value, and
J Ultrasound Med 2007; 26:875–883
Figure 1. During PDUS examination of the prostatic vasculature, the blood flow
in the capsular (arrow) and urethral (arrowhead) arteries was analyzed in the
largest transverse section of the prostate.
prostate volume. Group 1 included patients with
histopathologic findings of cancer in at least 1
lobe. Group 2 included patients with nonmalignant diagnoses such as BPH, acute or chronic
prostatitis, and high-grade prostatic intraepithelial neoplasia (HGPIN). Assuming that each lobe
of the prostate with either malignant or nonmalignant histopathologic findings was a single
unit, 110 lobes for 55 patients were further subdivided into groups A (malignant) and B (nonmalignant). Similarly, each unit was included in
group A in case the histopathologic diagnosis of
cancer was reported in either lobe, whereas
group B consisted of the units with the aforementioned nonmalignant diagnosis. These subgroups were compared statistically for the
means of the PI, RI, and S/D ratio measured at
the capsular and urethral arteries. In the study
group, a similar comparison of the lobes with
malignant and nonmalignant histopathologic
diagnoses on each side of the prostate for the
aforementioned Doppler indices was made.
Age data in the study group and in groups 1 and
2 are expressed as mean ± SD, and the results for
total PSA value and prostate volume are
expressed as median and interquartile range for
each group. The values for PI, RI, and S/D ratio in
groups A and B are expressed as mean ± SD.
Statistical analyses were performed with commercially available software (SPSS for Windows,
877
Power Doppler Ultrasonography of Prostate Gland Feeding Arteries
version 7.5; SPSS Inc, Chicago, IL). The comparison between groups 1 and 2 for mean age was
performed with the Student t test, whereas those
for the medians of total PSA value and prostate
volume were performed with the Mann-Whitney
U test. The comparisons between groups A and B
for the means of the PI, RI, and S/D ratio were
performed with the Student t test. Logarithmic
transformation was performed in case the distributions for the values of any of the aforementioned Doppler indices were not normal. P < .05
was considered statistically significant.
Results
The data for the number of patients and the
means for age, total PSA value, and prostate volume of the study group and groups 1 and 2 are
given in Table 1. No significant difference was
detected between groups 1 and 2 for age (P > .05).
Likewise, no significant difference was found
between groups 1 and 2 for median prostate volumes (P > .05, Mann-Whitney U test). However, a
marginally significant difference was detected
between groups 1 and 2 for the median total PSA
values (P = .051, Mann-Whitney U test).
With respect to the histopathologic outcome,
group 1 consisted of 14 patients with a diagnosis
of cancer, whereas group 2 consisted of 41
patients with benign histopathologic diagnoses
(19 with BPH and chronic prostatitis, 18 with
chronic prostatitis, and 4 with HGPIN). Group A
had 19 lobes with cancer, whereas group B had
91 lobes with nonmalignant histopathologic
findings (46 with BPH, 41 with chronic prostatitis, and 4 with HGPIN).
The comparison of groups A and B for the mean
PI, RI, and S/D ratio is given in Table 2. The mean
PI value for the capsular artery of group A (1.49 ±
0.57) was marginally lower than that of group B
(1.71 ± 0.52; P = .048, Student t test). In addition,
the mean RI value and S/D ratio for the capsular
artery of group A (0.78 ± 0.10 and 5.40 ± 2.74,
respectively) were lower than those of group B
(0.82 ± 0.08 and 7.40 ± 4.91) despite being statistically insignificant (P > .05 for each, Student t
test). However, the mean PI and RI values and
S/D ratio for the urethral artery of group A (1.71 ±
0.25, 0.81 ± 0.06, and 6.66 ± 3.35) were higher
than those of group B (1.56 ± 0.36, 0.80 ± 0.09,
and 6.37 ± 4.28) despite being statistically
insignificant (P > .05 for each, Student t test).
Comparisons of the lobes with malignant and
nonmalignant histopathologic findings on each
side of the prostate for the aforementioned
Doppler indices are given in Tables 3 and 4.
Thereby, logarithmic transformation for S/D
ratios of the capsular and urethral arteries was
performed because their distribution was not
normal. On the right side, the mean RI value for
the capsular artery of the malignant group (0.75
± 0.09) was marginally lower than that of the nonmalignant group (0.82 ± 0.09; P = .04, Student t
test). In addition, the mean PI value and S/D
ratio for the capsular artery of the malignant
group (1.46 ± 0.27 and 0.64 ± 0.17) were lower
than those of the nonmalignant group (1.80 ±
0.55 and 0.81 ± 0.27) despite being statistically
insignificant (P > .05 for each, Student t test).
However, the mean PI and RI values and S/D
ratio for the urethral artery of the malignant
group (1.71 ± 0.24, 0.81 ± 0.05, and 0.74 ± 0.11)
were higher than those of the nonmalignant
group (1.58 ± 0.35, 0.80 ± 0.09, and 0.73 ± 0.23)
despite being statistically insignificant (P > .05 for
each, Student t test). On the left side, the mean PI
and RI values and S/D ratio for the capsular
artery of the malignant group (1.58 ± 0.36, 0.81 ±
0.09, and 0.74 ± 0.20) were lower than those of the
nonmalignant group (1.75 ± 0.46, 0.82 ± 0.08, and
0.78 ± 0.25) despite being statistically insignificant (P > .05 for each, Student t test). However,
Table 1. Descriptive Clinical and Ultrasonographic Data for the Study Group and Groups 1 and 2
Parameter
Study Group
Group 1 (n = 14)
Group 2 (n = 41)
Age, y (mean ± SD)
tPSA, ng/mL (median, IR)*
PV, mL (median, IR)
66.45 ± 7.37
8.65, 8.12
65.00, 39.00
67.30 ± 7.16
11.65, 23.17
52.00, 32.25
66.17 ± 7.50
8.01, 6.23
67.00, 39.50
IR indicates interquartile range; PV, prostate volume; and tPSA, total PSA.
*A marginally significant difference was detected between groups 1 and 2 for the median of the total PSA value (P = .051).
878
J Ultrasound Med 2007; 26:875–883
Turgut et al
Table 2. Comparison of Groups A and B for Spectral Doppler Parameters From Capsular and Urethral
Arteries of the Prostate
Parameter
PIc (mean ± SD)
RIc (mean ± SD)
S/Dc (mean ± SD)
PIu (mean ± SD)
RIu (mean ± SD)
S/Du (mean ± SD)
Group A (n = 19)
1.49
0.78
5.40
1.71
0.81
6.66
±
±
±
±
±
±
0.57
0.10
2.74
0.25
0.06
3.35
Group B (n = 91)
1.71
0.82
7.40
1.56
0.80
6.37
±
±
±
±
±
±
0.52
0.08
4.91
0.36
0.09
4.28
P*
.048
.075
.119
.134
.279
.355
PIc indicates PI from the capsular artery; PIu, PI from the urethral artery; RIc, RI from the capsular artery; RIu, RI from the urethral artery; S/Dc, S/D ratio from the capsular artery; and S/Du, S/D ratio from the urethral artery.
*The difference between the mean PIc values of the 2 groups was statistically significant. No significant difference was
detected between the 2 groups for mean RIc, S/Dc, PIu, RIu, and S/Du values.
the mean PI and RI values and S/D ratio for the
urethral artery of the malignant group (1.78 ±
0.51, 0.83 ± 0.09, and 0.82 ± 0.24) were higher
than those of the nonmalignant group (1.63 ±
0.36, 0.80 ± 0.09, and 0.75 ± 0.21, respectively)
despite being statistically insignificant (P > .05
for each, Student t test).
Discussion
Because mortality caused by PCa increases with
advanced disease, much attention has been
given to its early detection. Previous PCa studies
in which gray scale TRUS was the initial imaging
modality used in early detection programs
revealed compromised diagnostic efficacy. This
was because of its poor ability to depict either
palpable or nonpalpable tumors10 and low positive predictive value for cancer detection11
despite providing enhanced visualization of the
anatomic detail of the gland. In the future, it is
evident that PCa can be expected to be detected
earlier by TRUS-guided prostate biopsy because
of the widespread use of PSA screening programs. Therefore, the PSA level correlating with
the stage and the volume of a tumor is one of
several factors limiting the visibility of the tumor
by gray scale TRUS examination.12 Benign prostatic hyperplasia is another factor that complicates the TRUS image by its mixed echo pattern,
which may mask any concurrent cancer,12 and
its compression effect on the peripheral zone
where tumors are best visualized by TRUS.13
However, other than the aforementioned factors, the isoechoic nature of a substantial proportion of contemporary PCa has become the
primary stimulus for the intense effort aimed at
improving the accuracy and incorporating modifications of TRUS in image-guided biopsy procedures. Importantly, most PCa is either
isoechoic10,12 or distinguishable only by a nonspecific irregularity of the echo texture.12
Table 3. Comparison of Right Prostate Lobes With Malignant and Nonmalignant Histopathologic Findings
for Spectral Doppler Parameters From Ipsilateral Capsular and Urethral Arteries
Parameter
PIc (mean ± SD)
RIc (mean ± SD)
S/Dc (mean ± SD)†
PIu (mean ± SD)
RIu (mean ± SD)
S/Du (mean ± SD)†
Malignant (n = 9)
1.46
0.75
0.64
1.71
0.81
0.74
±
±
±
±
±
±
0.27
0.09
0.17
0.24
0.05
0.11
Nonmalignant (n = 46)
1.80
0.82
0.81
1.58
0.80
0.73
±
±
±
±
±
±
0.55
0.09
0.27
0.35
0.09
0.23
P*
.076
.040
.074
.295
.530
.873
Abbreviations are as in Table 2.
*The difference between the mean RIc values of the 2 groups was statistically significant. No significant difference was
detected between the 2 groups for mean PIc, S/Dc, PIu, RIu, and S/Du values.
†Logarithmic transformation was performed because the distribution of the values was not normal.
J Ultrasound Med 2007; 26:875–883
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Power Doppler Ultrasonography of Prostate Gland Feeding Arteries
Table 4. Comparison of Left Prostate Lobes With Malignant and Nonmalignant Histopathologic Findings for
Spectral Doppler Parameters From Ipsilateral Capsular and Urethral Arteries
Parameter
PIc (mean ± SD)
RIc (mean ± SD)
S/Dc (mean ± SD)†
PIu (mean ± SD)
RIu (mean ± SD)
S/Du (mean ± SD)†
Malignant (n = 10)
1.58
0.81
0.74
1.78
0.83
0.82
±
±
±
±
±
±
Nonmalignant (n = 45)
0.36
0.09
0.20
0.51
0.09
0.24
1.75
0.82
0.78
1.63
0.80
0.75
±
±
±
±
±
±
0.46
0.08
0.21
0.36
0.09
0.21
P*
.297
.696
.532
.279
.419
.395
Abbreviations are as in Table 2.
*No significant difference was detected between the 2 groups for mean PIc, RIc, S/Dc, PIu, RIu, and S/Du values.
†Logarithmic transformation was performed because the distribution of the values was not normal.
On the basis of previous studies on angiogenesis showing that PCa tissue has increased
microvessel density compared with benign prostatic tissue,14–16 CDUS has been used in several
studies to detect areas of increased vascularity
within the gland suspicious for isoechoic hypervascular tumors, despite the fact that the relevant
finding could be associated not only with PCa
but also with prostatitis and BPH.1,17,18 In several
investigations focusing on the clinical utility of
PDUS, the technique has been found to
enhance PCa detection.19–24 However, research
by other authors17,25–27 revealed that the technique provided either no demonstrable benefit
for the detection of the disease or no substantial
improvement in specificity compared with conventional CDUS. Fortunately, recent advances in
ultrasonographic technology such as the introduction of ultrasonographic contrast agents and
elastography have been reported to be promising
for clinical utility.19,28
In a study by Kurjak et al29 in which the changes
in blood flow of the uterine artery secondary to
tumor angiogenesis were evaluated, the RI and
PI values of the uterine artery were found to be
lower in endometrial carcinoma. Similarly, a
recent prospective study by Obwegeser et al30
was based on the need for additional early detection strategies for breast cancer because of the
low sensitivity rate of mammography in dense
breasts, particularly in young women. They
investigated the value of spectral Doppler
parameters during CDUS of the lateral thoracic
(breast-feeding) arteries, which are the main
arteries to the breast. Importantly, the findings of
the study revealed that significantly lower values
880
for PI, RI, and S/D ratio were obtained in the lateral thoracic arteries of cancerous breasts in
comparison with the contralateral healthy
breasts, which was explained by the phenomenon that the growth of a vascular bed
within a cancerous breast would lower the
impedance of blood flow in the organ-supplying
artery. The authors concluded that the individual
differences in Doppler indices in women with
breast cancer might be useful indicators for the
diagnosis of breast lesions. In a recent study by
Delongchamps et al,31 it was reported that the
growth of PCa, like the growth of many solid
tumors, depends on angiogenesis, which has
been reported to be triggered by vascular
endothelial growth factor, resulting in increased
prostatic blood flow. We think that the increased
vascularization within a cancerous prostate lobe
may be expected to lower the impedance of
blood flow in the feeding arteries of the prostate,
as in breast cancer or endometrial carcinoma.
Little information has been found in the literature regarding the correlation of the pattern of
flow in the prostatic vasculature with various disease processes. To our knowledge, the spectral
Doppler analysis of abnormal areas of flow in the
prostate identified subjectively at CDUS was first
reported by Rifkin et al.1 Those authors reported
that the mean RI value of 0.579 (range, 0.45–0.80)
for cancer cases was slightly lower than the mean
values for cases with atypia, inflammation, and
benign disease, which were 0.601 (range,
0.49–0.86), 0.621 (range, 0.54–0.77), and 0.616
(range, 0.40–1.00), respectively, despite the fact
that no significant difference was detected
between the aforementioned histopathologic
J Ultrasound Med 2007; 26:875–883
Turgut et al
subgroups. Furthermore, it is noteworthy that a
considerable overlap was observed between the
reported ranges of RI values of the subgroups in
that study.
More information has been reported in the literature regarding waveform spectral Doppler
analysis of prostatic vessels out of any ultrasonographically detectable suspicious area.3,4,7,32–36
The mean RI values of arteries corresponding to
the peripheral zone and inner gland in healthy
subjects have been reported to range from 0.63
to 0.83 and from 0.64 to 0.76, respectively.3,4,31–33,36 The exact sites for the relevant blood
flow samplings ranged from the relatively proximal prostatic artery to the distal intraparenchymal branches. Among the authors, only Berger et
al32 included cases with PCa in their study group,
evaluating RI values and peak systolic velocities
in different zones of the prostate of patients with
PCa and BPH and healthy subjects. The respective mean RI values were 0.81, 0.84, and 0.83,
respectively, for the peripheral zone and 0.64,
0.77, and 0.66 for the transitional zone, which
revealed that the mean RI, in addition to the
mean for peak systolic velocity in the transitional zone, was significantly higher in patients with
BPH than in those with PCa and in healthy subjects. The slightly higher RI value for the urethral
artery (0.81) in our group of patients having PCa,
compared with that of patients with nonmalignant disease (0.80), seems contradictory to the
observation by Berger et al32 that a high RI in the
transitional zone is suggestive of BPH rather than
PCa. We think that the relevant discordance
between the two studies and the relatively higher RI values obtained in ours may be attributed
in part to the higher mean prostate volume of
our group of patients with PCa. The mean volume in our group was 54.9 mL compared with
39.8 mL for that of Berger et al,32 based on their
findings and those of several other authors33–36
who showed that the RI of the transitional zone
directly correlates with prostatic volume.
Another explanation for the contradiction in
the spectral Doppler measurements may be that
the sites for the relevant blood flow samplings
were not strictly the same in both studies. On the
other hand, we calculated a lower mean RI value
(0.78) for the capsular artery in patients with PCa
compared with patients with nonmalignant disJ Ultrasound Med 2007; 26:875–883
ease. Importantly, the mean RI value reported by
Berger et al32 for the peripheral zone arteries in
patients with PCa was 0.81, which was lower
than those of patients with BPH and healthy subjects, 0.84 and 0.83, respectively, despite the fact
that no significant difference was detected
between the groups in both studies. We think
that this difference in RI values may be attributed in part to the lowered impedance in the prostatic vessels of patients with PCa secondary to
the malignancy-associated angiogenesis.
Interestingly, RI values corresponding to the
arteries of the peripheral zone in our patients
with nonmalignant histopathologic findings
were higher than those corresponding to the
transitional zone vasculature in the same group,
although the latter would be expected to be higher secondary to BPH, with a mean prostate volume of 54.9 mL. We speculate that the finding
may be associated with the inhomogeneous
composition of our patients with nonmalignant
disease, comprising patients with the diagnosis
of chronic prostatitis as well as patients with
BPH, although no report regarding the impact of
chronic prostatitis on prostatic vasculature has
been found in the literature. Therefore, with
regard to histopathologic findings, it is noteworthy that in the study by Rifkin et al,1 the subgroup
of patients with the highest RI value measured at
the relevant site of abnormal flow was the one
with inflammation compared with those with
cancer, atypia, and benign disease.
In our study, a significant difference was detected between the groups with malignant and nonmalignant histopathologic findings for the
median total PSA value despite being marginal in
degree. Apart from the previously reported RI
value for the prostate vessels, to the best of our
knowledge, the association between both the PI
value and the S/D ratio and prostate histopathologic findings has not been reported previously.
Accordingly, we calculated a significantly lower
mean PI value of 1.49 for patients with PCa compared with 1.71 for those with benign disease.
This is in line with the lower values obtained for
the RI and S/D ratio in the former group, which
reflect the lower impedance due to the changes
in blood flow secondary to the increased blood
demand by the tumor tissue. Likewise, we calculated a significant difference between the RI val881
Power Doppler Ultrasonography of Prostate Gland Feeding Arteries
ues of the right prostate lobes with and without
cancer, which were 0.75 and 0.82, respectively.
We think that the lower RI value detected for the
left lobe with cancer and the lower PI value and
S/D ratio obtained for cancerous lobes on either
side confirm the aforementioned effect of angiogenic tumoral tissue on ipsilateral blood flow.
Finally, we conclude that spectral waveform
measurements by power Doppler TRUS may be
promising for the differentiation of PCa in
patients with benign diseases as an adjunct to
systematic sampling in the presence of ultrasonographically detectable lesions accompanied
by positive rectal examination findings and suspicious PSA levels. Moreover, we speculate that
the method would help in the follow-up of PCa
under radiation therapy by determining the
changes in prostatic blood flow. Further research
is needed to elucidate the potential of spectral
Doppler indices of the capsular and urethral
arteries to be associated with the current reference standard for PCa detection, the systematic
biopsy, particularly for those cancers with an
isoechoic texture indistinguishable from the
parenchyma on conventional gray scale TRUS,
where an increased number of biopsy cores on
the side with abnormal spectral Doppler index
values would be expected to enhance the PCa
diagnosis.
On the basis of our radiologic observations, we
suggest that power Doppler TRUS examination
of the feeding arteries of the prostate, as a novel,
noninvasive method, be included in the diagnostic workup of patients referred for prostate
biopsy, which, it is hoped, would enhance PCa
detection.
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